5-fluorouracil (5-FU), one of the most actively investigated anti-cancer drugs, is rapidly inactivated by the enzyme dihydropyrimidine dehydrogenase (DPD). ADH300004 blocks DPD. This study will test the safety and effects of oral ADH300004 14 hours prior to oral 5-FU in subjects with locally advanced, recurrent, or metastatic hepatocellular carcinoma.